1. Field of the Invention
The present invention relates to a film locating device for a microfilm camera which can be used for both roll-to-roll and roll-to-sheet systems.
2. Description of the Prior Art
In microfilming, information is recorded in small areas at high density by extremely fine images. In a microfilm camera for photographing information in such a fine area on the film, the photographic optical system is fixed, and it it thus important to position the film with high accuracy at a predetermined location with respect to the optical system. Further, in a 105 mm film, the information is recorded in several frames in the width direction, and the film must thus be moved in two directions. There is a microfilm camera called COM (computer output microfilmer) in which a computer output is recorded as a micro-image on the film. The computer output may be obtained directly from the computer, or it may be obtained indirectly from a magnetic tape after storage therein. In the former case, the computer output signal is converted into a CRT image and optically recorded directly on a film, or converted into modulated laser beams or electronic beams which are irradiated directly on the film by means of a two dimensional scanner and recorded as a microimage. The computer output has an extremely high speed, and it is therefore necessary to effect recording at a high speed in order to make good use of the computer time. To this end, it is necessary to record each frame at a high speed and at the same time to move or advance the film at a high speed between frames. Moreover, since the image frames are small and closely spaced, it is necessary to locate the film with high accuracy.
Various microfilm cameras are currently commercially available, but none of them are capable of functioning in both a roll-to-roll mode (in which the film roll is kept in its roll after exposure) and a roll-to-sheet mode (in which the film roll is formed into a sheet after exposure). In a COM, such a dual-mode camera is particularly needed. At present, a typical COM camera of the roll-to-roll type is disclosed in Japanese Patent Publication No. 14266/1974 filed by Terminal Data Corporation. In this camera a platen is moved in one direction and a film is fed in the other direction to locate the film. The platen can both hold and move the film. When this camera is used in a roll-to-sheet mode, however, several disadvantages are involved. First, since the tip of the film is moved on the platen, chips of film sometimes adhere to the surface of the platen which damages the film. Second, since the platen is moved in a condition where the tip of the film is not supported while projecting from the platen, the projecting portion of the film sometimes impinges upon other members to injure or damage the film. Further, since the film is fed by a drive roller only at the point where the film enters the platen, it is difficult to accurately locate the film.
A typical roll-to-sheet mode camera is disclosed in Japanese Patent Publication (OPI) No. 63722/1973. In this camera a magazine encasing an unused film roll is fixed on the platen, and the platen is moved in two directions to locate the film. After exposure, the tip of the film is gripped and pulled out to sever one sheet portion by a cutter. When this camera is used in a roll-to-roll mode, however, several disadvantages are involved. First, since the magazine is moved together with the platen, a large magazine cannot be used which limits the film length. Second, since the film must be passed through the cutter and film extracting mechanism, it is difficult to set the film. Third, since the film guide plate of the platen and the film extracting mechanism are limied to a 105 mm film, 16 mm and 35 mm films cannot be used.
Thus, the prior art roll-to-roll and roll-to-sheet mode cameras cannot be used interchangeably, which limits their adaptability.